The light module includes a wavelength conversion element, a first light source for emitting a first light beam (first primary light) in a first wavelength range onto the wavelength conversion element, and at least one second light source for emitting a second light beam (second primary light) in a second wavelength range onto the wavelength conversion element. The term light beam describes an incidence of primary radiation (excitation radiation), the emission of conversion radiation and the superimposition of non-converted primary radiation and conversion radiation to form a useful light. Primary radiation denotes the excitation radiation of the primary light sources, in particular the radiation that is incident on a wavelength conversion element. The wavelength conversion element is also referred to hereinafter as phosphor element. Primary light sources are light sources used for the excitation (conversion) of the phosphor. In the present case, the primary light sources are e.g. the first light source and/or the at least one second light source.
The first wavelength range and the at least one second wavelength range differ in their dominant wavelength. The dominant wavelength is also referred to as dominance wavelength. This term can be used for laser diodes and LEDs, and also for the conversion properties of phosphor. The dominant wavelength of light of a light color (colored light) is defined in the CIE chromaticity diagram (standard chromaticity diagram) by the point of intersection between the straight line extended from the white point via the determined color locus of the colored light and the spectrum locus of the closest perimeter of the CIE chromaticity diagram. By way of example, efficient red phosphors have a dominant wavelength of approximately 600 nm. The term dominant indicates what color impression is imparted to the human eye by a light emitting diode. The dominant wavelength is also referred to as perceived wavelength or a hue-identical wavelength.
A wavelength-converted part of a primary light that is emitted by a wavelength conversion element or phosphor is referred to as conversion light. The latter is emitted by the phosphor element as a conversion light beam. The present wavelength conversion element is configured to convert the primary light radiated in by the first light beam at least partly into a first conversion light and to convert the primary light radiated in by the at least one second light beam at least partly into second conversion light. If the at least two primary light sources radiate onto the same area of a conversion element having a homogeneous phosphor composition, the first conversion light and the second conversion light do not differ or substantially do not differ. In the general case, the at least two primary light sources can radiate onto different areas of the conversion element. If the conversion element then differs in its phosphor composition with regard to these two areas of incidence, the first conversion light and the second conversion light can have different spectral properties (spectral distribution). In particular, the conversion element has a homogeneous composition, that is to say that the first conversion light and the second conversion light are spectrally identical or substantially spectrally identical. The term spectral distribution denotes the intensity distribution of a radiation over various wavelengths.
The primary light beam (that is to say the first and second light beams) in this case need not impinge on the phosphor simultaneously, rather the respectively assigned primary light sources can be operated for example in a manner clocked with a temporal offset, e.g. also in a push-pull fashion. The primary light beams also need not impinge congruently on the same area of incidence of the phosphor, but rather can regionally only partly overlap or even be completely disjoint. They can also be radiated onto different sides of a phosphor element. The same analogously applies to the conversion light beams. In particular, the two primary light beams impinge on the same area of incidence and overlap completely or substantially completely.
At least the first conversion light and the second conversion light form a third light beam. In the case of a complete conversion, no primary light emerges from the wavelength conversion element. In this case, in particular only the first conversion light and the second conversion light form the third light beam. In the case of the transmissive arrangement in partial conversion as preferred here, part of the unconverted primary radiation emerges from the wavelength conversion element. In the case of a partial conversion, therefore, the mixed light (useful light) results from the superimposition of unconverted primary radiation and conversion light. Given the presence of two primary light sources having different dominant wavelengths in a transmissive phosphor arrangement, the total mixed light is composed of the superimposition of unconverted first primary radiation and first conversion light and also unconverted secondary primary radiation and second conversion light. In this case, preferably, the first conversion light and the second conversion light together with the unconverted first primary light and the unconverted second primary light form the third light beam. In this case, the first conversion light and the second conversion light can have different dominant wavelengths. It is preferred, as explained above, for the first conversion light and the second conversion light not to differ or substantially not to differ spectrally.